It is conventionally known for vehicle antennas to cover a rod-like antenna element by means of an antenna cover made of a resin member for protection. One possible method for manufacturing such an antenna cover is integral molding using a mold and an antenna element. This is a method in which the antenna element is inserted into a mold for forming an antenna cover and then a resin is poured therein. An antenna cover thus manufactured is expected to exhibit high protection performance since the antenna element can be integrally covered from tip to base.
On the other hand, designs of vehicle antennas are deeply researched for to cope with marketing demands. Elements that determine design are considered to be shape, color and pattern, and it is possible to bring diversity to design on the vehicle antenna by, for instance, defining the shape of the antenna rod (that is, a portion of the rod-like antenna element mounted to the antenna base which is covered by the antenna cover) of the vehicle antenna to be conical or of triangular pyramid shape or fitting a cap to the antenna cover covering the antenna element that is of different color than that of the cover.
It is usually that vehicle antennas are weather-beaten over an extended time period and they are also often vandalized. When assembling the antenna rod by fitting a cap onto an antenna cover which covers an antenna element, it is necessary to improve the strength of the cap or the cover so as to prevent cases in which the cap comes off from the antenna cover.
For instance, Japanese Patent Laid-Open Publication No. 2005-191656 (referred as “patent document 1”) discloses an antenna for portable wireless use which can be simply and easily fixed to a body without using any adhesive and from which ornamental cap does not come loose to make its appearance worse even after a long term of use. This antenna is arranged in that a joint is connected to an upper end of a whip element and in that a cap is overlaid onto an upper end of the joint, wherein a projection is formed on the cap side while a hole is formed on the joint side for fitting in overlaying the cap on the joint.
While the antenna for portable wireless use according to Patent Document 1 improves the design of the entire antenna by using an ornamental cap and is provided with a projection and a hole on the cap and the antenna, respectively, for preventing falling off of the cap, such fixation provided by the projection and the hole may be affected when force is applied from the exterior of the antenna so that the cap falls off.
In view of the above circumstances, it is an object of the present invention to prevent falling off of a cap in a vehicle antenna of a type in which a cap is fitted onto an antenna cover that covers the antenna element for protection.